How much formula to give question

I’m looking to switch some of lb’s feeds to formula but don’t know how much to offer because frankly he would drink until he bursts Example routine below 1.30am boob 7am boob 9am formula top up before nap 10.30am boob 1pm formula 3.30pm boob 5pm boob 6.30pm bottle 8oz My question is how much formula for the two feeds in the late morning early afternoon? He’s 6 months, 92nd centile and eating some solids (fruit/veg) TIA